Stabilized iron pentacarbonyl and motor fuel containing the same



Patented Jan. 3, 1950 STABILIZED IRON PENTACARBONYL AND MOTOR FUEL CONTAINING THE SAME Robert Edward Christ, Elizabeth, N. 1., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 21, 1946, Serial No. 671,398

16 Claims.

This invention relates to liquid fuels suitable for use in internal combustion engines. More particularly, it relates to the use of iron pentacarbonyl as an anti-knock agent in motor fuels and to iron pentacarbonyl of improved stability to light and air.

It is known that iron pentacarbonyl possesses the property of raising the octane value of gasoline. It is ideal in many respects as an antiknock, a very small amount, less than 0.1% by volume, being sufficient to raise the octane rating of gasoline to a high value. It is very soluble in gasoline, substantially inert with respect to the parts of the engine with which it comes in contact, and in concentrated or diluted form does not cause poisoning on contact with the skin.

Despite its many advantages, iron pentacarbonyl, Fe(CO) 5, has not attained commercial success as an anti-knock agent due to its inherent instability to light by which it is rapidly decomposed, this decomposition being most rapid in sunlight or blue light and least so in red light. The decomposition is a progressive change, the first product being iron enneacarbonyl, Fez(CO) 9, which comes down in the form of glistening golden-yellow plates according to the following reaction,

followed by a further decomposition with production of a voluminous black precipitate of ferrous oxide and other iron compounds.

This decomposition not only results in loss of octane value from the initially high level obtained in the gasoline with the freshly dissolved iron pentacarbonyl but also renders the gasoline unfit as a motor fuel due to the propensity of the precipitate to clog the gasoline line or the carburetor.

I have now found that motor fuels of high quality, which in the presence of sunlight and air exhibit a high degree of permanency in respect to anti-knock characteristics and freedom from formation of precipitates derived from the antiknock agent, may be obtained from gasoline of low octane value and iron pentacarbonyl by employing in conjunction with the latter certain substances, hereinafter more particularly defined, which act as stabilizers for the iron pentacarbonyl.

*The present invention resides in my discovery that iron pentacarbonyl may be rendered substantially permanently resistant to decomposition by light and air when there is intimately associated therewith a hydrocarbon-soluble substance which is a saturated aliphatic hydroxy polycarboxylic acid neutral aliphatic ester free from acidic groups, acidified with a hydrocarbon-soluble carboxylic acid.

The term neutral as used herein with reference to the aliphatic esters is employed in the usual sense to denote that all of the carboxyl groups of the hydroxy polycarboxylic acid portion of the aliphatic ester molecule are in the for!" of ester groups, none being in the free state.

For the acidification of the neutral aliphatic esters, the amount of the hydrocarbon-soluble carboxylic acid generally need not exceed 9. volume equal to that of the neutral aliphatic ester, only sufficient being employed to bring about the acidification. A preferred group of acids for this purpose are the long chain fatty acids, for example, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, ricinoleic acid, etc. Naphthenic acids as obtained from the oxidation of petroleum,

Fischer-Tropsch acids and rosin acids also may be used.

For improving the stability of iron pentacarbonyl to light and air, the acidified neutral aliphatic esters may be employed in widely varying amounts, ranging from about 1% to about 50% by volume on the iron pentacarbonyl. The amount necessary in each instance to render the iron pentacarbonyl substantially permanently stable to light and air may vary with the individual acidified neutral esters, but, in general, it will be about 5 to 10% by volume on the iron pentacarbonyl.

In the practice of the invention for the preparat ion of motor fuels of increased anti-knock characteristics the iron pentacarbonyl, which is a liquid, and the stabilizer are simply dissolved in the gasoline or other liquid base fuel to be treated, the mixture being stirred to insure uniformity in dispersion of the iron pentacarbonyl and the -stabilizer therein. The iron pentacarbonyl, it-

self, is employed in amounts of 1 to 4 cc. or more per gallon of the liquid motor fuel, a preferred proportion based on a gasoline of 60-65 octane number being from 3 to 4 cc. per gallon of the gasoline. It will be understood, of course, that the proportion of iron pentacarbonyl used will depend on the initial octane value of the liquid fuel to be treated and as well on the level to which this value is to be lifted by the treatment. Generally, the lower the octane rating of the liquid 3 fuel, the greater should be the proportion of iron pentacarbonyl added thereto.

The iron pentacarbonyl and stabilizer may be added separately to the liquid fuel or, as is preferred, they 'are added. together from aconcentrate which is a blend of the iron pentacarbonyl, the stabilizer, and a small proportion of a mutual organic solvent therefor which is compatible as an ingredient of the liquid motor fuel, suitably, a portion of the liquid fuel of the kind to be treated. The stabilized concentrate may be stored over long periods of time without volumes of the two, although this proportion may be varied somewhat where particular concentrations of iron pentacarbonyl are desired.

The motor fuels which may be treated with the stabilized anti-knock agent for improvement in octane value may be any of the usual liquid hydrocarbon fuels such as kerosene, gasolines, straight-run, cracked or so-called poly gasoline, or blends of these with benzol, alcohol or the like, diesel fuels of the Fischer-Tropsch type,

or other types, such as alcohols, in which the iron pentacarbonyl andstabilizer are soluble.

By the term hydrocarbon-soluble as used herein is meant that the substance so-designated is soluble in kerosene, gasoline, benzol and the like liquid hydrocarbons.

As a specific example of stabilized anti-knock concentrates which may be prepared in accordance with the invention is the following composition in which was blended in the preferred manner, by volume,

1 part oleic acid 1 part trioctyl citrate 22 parts gasoline 20 parts iron pentacarbonyl When mixed with a gasoline of octane number 65 in the proportion of 8.8 cc. to the gallon of gasoline, the mixture represents a motor fuel of 75 octane number which retains its high antiknock quality over long periods of time on exposure to air or sunlight.

Further illustrative of the neutral aliphatic esters which in conjunction with a hydrocarbonsoluble carboxylic acid may be employed in accordance with the invention for improving the stability of iron pentacarbonyl to light and air.

are, for example, the hydrocarbon-soluble neutral esters of l-hydroxy glutaric acid, 2-hydroxy glutaric acid, 2-hydroxy glutamic acid, l-hydroxy adipic acid, 4-hydroxy azelaic acid, 2-ethyl malic acid, malic acid, tartronic acid, tartaric acid, citric acid, isocitric acid, hydroxy citric acid, l-hydroxy-l-carboxysuccinic acid, l-hydroxybutane-1,2,3-tricarboxylic acid, l-hydroxybutane- 1,2,4-tricarboxylic acid, 3-hydroxybutane-l,1,5- tricarboxylic acid, 2-hydroxy-4-methylpentane- 1,1,2,4-tetracarboxylic acid and LG-dihydroxyhexane-2,2,5,5-tetracarboxylic acid, etc., or of mixtures of these acids,where the ester groups are derived from one or more aliphatic monohydric alcohols having at least 4 carbon atoms.

for example, 2-ethylbutanol,- methyl amyl alco-' hol, hexanol, heptanol-2, octanol-l, Z-ethylhexanol, undecanol, dodecanol, tetradecanol, heptadecanol, octadecanol, oleyl alcohol, cyclohexyl alcohol, 2-aminobutanol-l, 4-amino-bu tanol-l, n-butyl alcohol, tertiary butyl alcohol, 4-ch1oro-n-butyl alcohol, l-bromo-Z-hydroxy butane, etc. Preferably, the ester groups contain the longer chain hydrocarbon radicals, for example, of about 8 or more carbon atoms, as the longer the hydrocarbon chain thereof, generally,.

the greater the hydrocarbon solubility of the neutral ester molecule.

The neutral aliphatic esters may be prepared in accordance with known methods for the esterification of carboxylic acids. A preferred group of the hydroxy polycarboxylic acids for the preparation of the neutral esters are citric, malic, tartaric and tartronic acids, preferred,

' however, only from the standpoint of ready availremoval of the residue of the iron pentacarbonylability from natural sources. Other preferredsaturated aliphatic hydroxy polycarboxylic acids are those containing a plurality of hydroxy groups, such as hydroxy citricacid.

In additionto their action as stabilizers for the iron pentacarbonyl in the motor fuel, the acidified neutral esters favorably influence the from the internal combustion engine. In this respect, it has been observed that the residue is almost completely removedfrom the combustion areas of the engine and emerges from the exhaust as a light, fluify red powder.

As various other embodiments of the invention will occur to those skilled in the art, it is not intended that the scope of the patent be limited except as is required by the prior art and the appended claims. i

I claim:

1. A composition comprising iron pentacarbonyl blended with from about 1 to about by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of a satu- -rated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groupscontains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbon-soluble carboxyiic acid.

2. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of citric acid in which the hydroxy'portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a. hydrocarbon-soluble carboxylic acid.

3. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups conequal volume of a asaavra and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester.

being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

5. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of trioctyl citrate acidified with a volume of a long chain fatty acid not exceeding that of the trioctyl citrate.

6. A motor fuel comprising a liquid base fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

7. A motor fuel comprising aeliquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic ac d.

8. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of citric acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an hydrocarbon-soluble carboxylic acid.

9. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

10. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkyl ester oftartaric acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms,

the alkylester being acidified with'no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

11. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of trioctyl 7 citrate acidified with a volume of a long chain gay acid not exceeding that of the trioctyl cit- 12. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidiied hydrocarbon-soluble neutral alkylester of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy ortion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid, and an amount of a liquid hydrocarbon solvent sufficient to dissolve the pentacarbonyl and the acidified alkylester.

13. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of citric acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms,

the alkylester being acidified'with no more than an equal volume of a hydrocarbon-soluble carboxylic acid, and an amount of a liquid hydrocarbon solvent suflicient to dissolve the pentacarbonyl and the acidified alkylester.

14. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of. an acidified hydrocarbon-soluble neutral alkylester of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbonsoluble carboxylic acid, and an amount of a liquid hydrocarbon solvent sufiiclent to dissolve the pentacarbonyl and the acidified alkylester.

15. A stabilized iron pentacarbonyl concentrate. consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester of tartaric acid in which the hydroxy portion is free and the alkyl radical'of each of the ester groups contains at least 4 carbon atoms, the alkylester being acidified with no more than an equal volume of a hydrocarbonsoluble carboxylic acid, and an amount of a, liquid hydrocarbon solvent sufiicient to dissolve the pentacarbonyl and the acidified alkylester.

16. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of trioctyl citrate acidified with a volume of a long chain fatty acid not exceeding that of the trioctyl citrate, and an amount of a liquid hydrocarbon solvent sufllcient to dissolve the pentacarbonyl and the acidified trioctyl citrate.

; ROBERT EDWARD CHRIST.

REFERENCES CITED Name Date 1,995,615 Jaeger Mar. 26, 1935 2,149,221 Lamping Feb. 28, 1939 2,397,332 Amott Mar. 26, 1946 

1. A COMPOSITION COMPRISING IRON PENTACARBONYL BLENDED WITH FROM ABOUT 1 TO ABOUT 50% BY VOLUME ON THE PENTACARBONYL OF AN ACIDIFIED HYDROCARBON-SOLUBLE NEUTRAL ALKYLESTER OF A SATURATED ALIPHATIC HYDROXY POLYCARBOXYLIC ACID IN WHICH THE HYDROXY PORTION IS FREE AND THE ALKYL RADICAL OF EACH OF THE ESTER GROUPS CONTAINS AT LEAST 4 CARBON ATOMS, THE ALKYLESTER BEING ACIDIFIED WITH NO MORE THAN AN EQUAL VOLUME OF A HYDROCARBON-SOLUBLE CARBOXYLIC ACID. 